In the U.S. alone, there are approximately 1.4 million individuals who use wheelchairs full time. These individuals have functional impairments for various reasons and are affected at various levels. Depending on the type and level of impairments, the wheelchair seating requirements can be complex. Among those who use wheelchairs regularly, individuals with spinal cord injured (SCI) at the cervical level have altered neuromuscular control, requiring sophisticated seating devices that provide postural stability while permitting functional independence. Independence from the seated position is a primary concern. Additionally, as these individuals use wheelchairs full time, prevention of progressive spinal deterioration and deformity from prolonged sitting is of paramount importance.
Current strategies for wheelchair prescription include devices that provide stability, comfort, and functional independence/mobility, but also that assist in the prevention of the negative biomechanical spinal alterations that occur from prolonged sitting. However, these goals are often in conflict with each other and current devices rarely achieve all of these goals simultaneously. Accordingly, there is a need to successfully maximize all of these factors in one comprehensive seating device.
Pelvic support can be influenced at four regions: inferior, lateral, anterior, and posterior. The base of support (inferior support) for the pelvis is usually provided by the seat cushion. Lateral pelvic support is achieved through separate blocks or wedges that are either a component of the seating system or attached to the wheelchair. Anterior support is currently achieved through hip or lap belts. However, these devices are known to restrict movement of the user and impose high loads on the abdominal cavity. Posterior support is determined by the shape of the back support and the lumbar pad. Because these supportive devices are, in general, rigidly attached to the seating system, and are designed to be adjusted or removed by the caregiver, they tend to restrict the user to a fixed position.
Thoracic level support is generally achieved through lateral thoracic supports. Although these devices are available in various sizes and materials, they are typically mounted to the back support or backposts of the wheelchair, further restricting the user to a fixed position. To be effective, these devices must make intimate contact with the trunk. However, as trunk mobility is necessary to perform functional activities, these devices often need to be released. Although current lateral thoracic supports have “swing-away” or removable features, adjustment of these supports usually requires the assistance of the caregiver. Furthermore, these rigid, fixed devices may cause respiratory difficulty and soft-tissue irritation.
Thus, current seating designs often result in a compromise between user stability and functional independence. In wheelchair seating assessments and fittings, a compromise is made to find a posture that is the most tolerable and functional for the user—one which allows the user mobility necessary to accomplish activities of daily living (ADL), yet still provides enough stability to accommodate weak or paralyzed muscles. Unfortunately, as a result of the interference of these supportive devices on user function, many wheelchair users opt not to use these supportive devices, thereby exposing themselves to the negative effects of unsupported sitting.
Thus, a sacral/pelvic stabilizing device that provides pelvic support while allowing simple user adjustment to allow movement, independent of a caregiver, and prevents pressure overload of the abdomen would be a significant improvement. Similarly, a thoracic support device which provides thoracic support while allowing simple user adjustment to allow movement, independent of a caregiver, and which does not cause respiratory difficulty or soft-tissue irritation also would be a significant improvement.
As stated previously, SCI individuals who use wheelchairs full time, are susceptible to the negative consequences of prolonged sitting, which not only includes PU formation, but spinal degeneration from prolonged spinal loading. Additionally, studies demonstrate that wheelchair users are exposed to unacceptable levels of whole body vibration (WBV) when propelling over uneven surfaces. As current seating systems do not permit movement of the back support relative to the seat cushion as the wheelchair propels over uneven or rugged terrain, the user's body is subject to elevated levels of WBV. Thus, it can be seen that improved design of the seat and back support may reduce WBV.